Many oral appliances, including dental aligners, are worn in the oral cavity and may interact with oral structures for therapeutic or cosmetic effects. For example, dental aligners are worn on the teeth to apply force to straighten the teeth. Oral appliances may be custom formed to fit the patient's teeth and oral cavity. However, measuring the fit and interaction between an oral appliance and oral structures, such as teeth, may be difficult.
Scanning may be used to examine the shape of an oral appliance or of oral structures, however it is difficult to simultaneously examine both the appliance and the teeth or other oral structures when the appliance is in place. Typical optical intra-oral scanners capture only the first surface encountered in the line of sight. The surfaces of the teeth and portions of the appliance are hidden, preventing examination of their interaction. CT scanning uses X-rays which can penetrate many materials, but with which it is difficult to simultaneously image both plastic features of a dental appliance and the teeth due to their widely different opacity to X-rays. Furthermore, these X-rays are harmful to the patient. Other techniques such as filling gaps between the appliance and the teeth with colored gels do not provide quantitative measurements and are subject to large errors and usage problems.
Thus, there is a need for methods and apparatuses that may be used to examine both an oral structure (such as the teeth) and an appliance worn on the oral structure, and particularly the interaction between the two, while the appliance is being worn by the patient. Described herein are methods and apparatuses that may address this need.